Regarding the wattage being changeable from the main screen.
I like it being that way. Why?
I vape two flavors in two 'identical' tanks. One works best at say 30W, the other works best at say 25W.
When I swap tanks, I read the resistance and then play with the wattage a bit to get the vape I like.
As long as the wattage is still changeable from the main screen when not Playing, cool. If it were read only while Playing, fine. No reason to change your 'perfect' puff after all.

I think Gauges has its own personality and doesn't at all 'feel' like the Material-ish themes. Because, well, gauges.
With the current changes and the addition of the Material-ish UI, I use Gauges. With the old UI, I did not.
Default the new UI.

No official doc's/video's of how it works as of yet. From the Datasheet (linked below) it says:
Replay
Replay is a new feature introduced on the DNA 250C. Replay is intended to capture the flavor and satisfaction of the “perfect puff” and provide the same level of performance and consistency on all subsequent puffs. The use of Nickel, Stainless, Titanium, or other material that increases in resistance when heated is required. In addition, Replay will also prevent dry hits when used with wattage control.
To use Replay set the device to the desired power level and operate it normally. Once a satisfying puff is achieved, activate the feature to save and replay the saved puff each time the device is fired. Puff length is not a factor and the user will not be limited to the length of the previous puff. Disable Replay to resume normal operation or find a new puff to save. If Replay cannot be enabled the coil is not compatible.
250 Color Datasheet
https://downloads.evolvapor.com/dna250color.pdf
With every revision of your themes it just gets better !

Hey thanks man
Temp goes away by design. Turns out when you save a puff and start replaying you're not supposed to adjust either the wattage or the temp. I know changing the temp doesn't do anything at all, changing the wattage does change the vape but I'm not sure what other aspects of replay it affects. I'll be testing this in the next few days.
If you still want to add a temp field open up the theme editor, follow the screenshot and choose "Setting -> Atomizer -> Coil Temperature"